Construction of NiS/carbon fibers confined NiS composite: high catalytic activity for enhancing the hydrogen storage performances of MgH2

To effectively enhance the catalytic activity of NiS, NiS particles confined into carbon fibers were prepared by electrostatic spinning followed pyrolyzation and NiS particles decorating was performed by further hydrothermal loading. The decorated NiS exhibits particle (NiS@PAN-NiS) and needle-like (NiS@PAN-NiS*) morphologies. After adding the catalysts into MgH₂, the synthesized MgH₂-5 wt% NiS@PAN-NiS composite can absorb 2.6 wt% hydrogen at 353 K and release 5.0 wt% hydrogen within 1 h at 573 K. The initial hydrogen desorption temperature was reduced to 539 K. The activation energies for hydrogen absorption/desorption were greatly reduced to 66.76 and 89.95 kJ mol⁻¹, respectively. The method of confining by electrospinning and particle decoration by hydrothermal loading reduce NiS particle agglomeration. The Mg₂Ni/Mg₂NiH₄ hydrogen pump formed by reaction between NiS and MgH₂ effectively enhanced hydrogen absorption and desorption kinetics. The formed MgS also improved the catalytic activity on the transformation of Mg and MgH₂. Moreover, the carbon fibers should influence the contact between in situ formed MgS and Mg₂Ni, providing more catalytic sites and hydrogen diffusion pathways. The construction of NiS/carbon fibers confined NiS composite by carbon fibers derived from pyrolyzation as medium provides considerable way for designing NiS-based catalysts to enhance the hydrogen storage performances of MgH₂.

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